Direct dynamics study on the reaction of O(3P)+PH3→PH2+OH

A direct ab initio dynamics study of thermal rate constants is presented for the hydrogen abstraction reaction of O(P-3) + PH3-> PH2 + OH. The UQCISD/6-311 + + G(d,p) method was employed to optimize geometry structures and to calculate the minimum energy path (MEP). Frequencies for all stationary points were obtained at the UQCISD/6-311++ G(d,p) and UQCISD(T)/6-311 + + G(2df,2pd) levels of theory, respectively. The energies of the stationary points and 22 points selected along MEP were refined at the UQCISD(T)/6-311 + + G(2df,2pd)//UQCISD/6-311 + + G(d,p) level of theory. Reaction rate constants were evaluated by using the conventional transition state theory (TST), the canonical variational transition state theory (CVT) and the CVT with the small curvature tunneling correction method (CVT/SCT) over the temperature range of 200-2000 K, respectively. The results show that the classical potential barrier Delta E-not equal and the reaction enthalpy Delta H-298(0) calculated are 3.35 and - 19.44 kcal/mol, respectively, for title reaction. The variational effect is significant in the whole temperature range, while the SCT tunneling correction is important within the temperature range of T:! 500 K for the calculation of rate constant. (c) 2004 Elsevier B.V. All rights reserved.